The following meanings for the abbreviations used in this specification apply:
APN Access Point Name
BSC Base Station Controller
BSSGP Base Station Subsystem GPRS Protocol
DSCP DiffServ Code Point
GERAN GERAN GSM/EDGE Radio Access Network
GGSN Gateway GPRS Support Node
GPRS General Packet Radio Service
GSM Global System for Mobile communications
GTP GPRS Tunneling Protocol
GTP-U GTP-User plane.
GW Gateway
IP Internet Protocol
PDN Packet Data Network
PDN-GW Packet Data Network Gateway (also P-GW)
PDP Packet Data Protocol
PMIP Proxy Mobile IP
S-GW Serving Gateway
TDF Traffic Detection Function
UE User Equipment
3GPP is currently working on “Service Identification for RRC Improvements in GERAN” (SIRIG). It is envisioned that the core network informs the GERAN radio network when downlink IP packets relating to specific applications are detected via deep packet inspection within the core network. The GERAN radio network will use this information to configure radio bearers according to the needs of the detected applications, e.g. by assigning a suitable number of timeslots for the bandwidth requirements of the application.
Within the core network, the deep packet inspection will either be performed by a GGSN/PDN-GW or by a standalone Traffic Detection Function (TDF) (see TS 23.203).
It has been agreed within 3GPP CT4 as a working assumption that the GGSN/PDN-GW using the GPRS Tunneling Protocol (GTP) (TS 29.060) will transfer the information towards the SGSN within a new extension header within the GTP user plane packets used to transfer the user plane relating to the specific application. If a standalone TDF is used, it will transfer the information to the GGSN/PDN-GW as DiffServ Code Point (DSCP) marks within the IP header of the inspected user plane packets and the GGSN/PDN-GW provides an interworking to GTP-U.
A GGSN using Proxy Mobile IP (PMIP) will transfer the information to the Serving-GW as DSCP marks within the IP header of the inspected user plane packets, and the Serving-GW will forward the information towards the SGSN within a new extension header within the GTP user plane packets used to transfer the user plane.
The SGSN will transfer the information on to the GERAN BSC using an extension of the Base Station Subsystem GPRS Protocol (BSSGP) (TS 48.018).
3GPP is also studying improvements for IP traffic handling for other radio networks than GERAN and might thus decide to use the new GTP-U header extension towards other radio networks in the future.
The DSCP header is a mandatory part of the IP header and always present. It is normally used for requesting priority treatment within IP routers.
The new GTP-U header extension, as described above, will increase the overall size of a GTP-U package by 8 byte and thus lead to extra bandwidth requirements where GTP is used. If the DSCP IP header is always interworked, the new GTP-U extension header will also be supplied for user plane packets that do not relate to applications that require special treatment, which leads to an unnecessary waste of resources.